Process for making fabric from bulked yarn



United States Patent 3,128,527 PROCESS FOR MAKING FABRIC FROM BULKED YARN Francis Schulz, Keith Jarnell, and Arthur M. G. Kinnear,

all of I-Iarrogate, England, assignors to Imperial Chemical Industries Limited, London, England, a corporation of Great Britain No Drawing. Filed Nov. 23, 1960, Ser. No. 71,177 2 Claims. (Cl. 28-72) This invention relates to bulked filament yarns made from synthetic thermoplastic polymers and fabrics made from such bulked yarns.

Recently many methods have become known for the making of bulked yarns from synthetic thermoplastic polymer filaments which have many desirable and unusual properties. Preferred methods for making bulked yarns are described in British specifications 777,625, 808,- 213, 881,729, 887,729 and 921,583. They suifer from the disadvantage, however, that individual filaments have a tendency to become caught during handling of the yarn, or during wear of fabrics containing such bulked filament yarns, with the result that neighbouring filaments or yarn become pulled together before they break. Quite minor accidental occurrences of this type make the whole fabric or garments made therefrom, unsightly. The effect is not unlike the well known snagging of ladies nylon filament yarn stockings. In the latter case, however, snagging usually involves the whole yarn, not individual filaments. Snagging of the filaments may be largely overcome by inserting twist in the yarn or by suitable finishing treatments. In the case of bulked filament yarns the insertion of twist reduces the desirable bulk, the soft handle and covering power of the fabrics. Finishing methods are also only partially successful. The reduction of bulk is usually undesirable because of the very nature of the bulked filament yarns. In the bulked yarns, loops of individual filaments project from the main body of the yarn and it is difficult to prevent them from being caught during handling and in wear.

We have found that the effect becomes worse with increasing strength of the filaments. It may also be linked to some surface phenomenon on the filaments, associated with their surface frictional characteristics. When the strength of the filaments is deliberately reduced in controlled manner, without, however, appreciably affecting other desirable properties, such as recovery from bending, bulked yarns and fabrics are obtained, in which the tendency to snagging is considerably reduced. Certain changes of the surface friction characteristics e.g. by'imparting a large surface area to the filaments compared with the spun and drawn condition, also tends to reduce snagging.

Snagging, like many phenomena encountered during daily use of textile fabrics, such as handle, warm feel, creasing, pilling, wear and abrasion resistance and the like, depend on a subjective assessment and are diflicult to express in reproducible and measurable terms. Attempts have therefore been made to measure certain physical and mechanical properties which, after many wearer trials, can, to some extent, be correlated and give a measurable indication regarding the actual wear behaviour of the fabric. The correlation of a subjective assessment 3,128,527. Patented Apr. 14, 1964 such as good handle in these terms, however, defies solution.

We have carried out tests which indicate that snagging of bulked filament yarns can, to some extent, be correlated with the abrasion resistance of the fabric. It will, of course, be appreciated that incidental damage which causes snagging, for example, when one of a number of filaments gets caught on ones finger nail, or some rough object, is not necessarily reproduced by an artificial abrasion test.

In the abrasion test, unlike the accidental snagging during wear, the filaments in the bulked yarn become broken and they become entangled with neighbouring broken filaments to form small agglomerates of fibers, reminiscent of the pill formation encountered in fabrics made from staple fibres. The agglomerates in our case are much smaller in size and, moreover, on the fabric made from low tenacity filaments, they are automatically removed as the test or wear continues.

According to our invention, therefore, we provide knitted or woven fabrics with improved wear properties, made from bulked filament yarns from synthetic thermoplastic polymers which have a deliberately reduced strength compared with commercially available bulked yarns, such that the tenacity of the individual filaments, when measured at intervals of not more than inch, is between 1 and 3.5, preferably 2.0-2.9 grams per denier. The yarn crimp elongation is preferably less than 15%, and the shrinkage per unit length, in hot water or steam, preferably does not exceed 10%.

The strength of the yarn may be reduced in a number of ways, provided that it is carried out in a controlled manner.

The filaments may be weakened either uniformly or non-uniformly, but in any case, so that the tenacity is within the specified limits. It will be appreciated that the filaments may have a somewhat higher tenacity at smaller intervals than inch, i.e. stronger portions may break under a load greater than 3.5 grams per denier. Since, however, the weaker portions determine the overall strength of each filament, the tenacity at greater intervals than inch should be between 1 and 3.5 grams per denier, preferably 2-2.9 grams per denier.

The range of deniers of the filaments in commercially available synthetic filament yarns which are suitable for bulking processes, range from about denier to 4, the preferred deniers being 1-3 per filament and with a tenacity of about 4.5 grams per denier or more, as in the :ca'se of nylon and polyethylene terephthalate filaments. 50 a higher denier are used, their strength must be reduced to It will be appreciated therefore that if filaments of a a greater extent, compared with the commercially available filaments, than when a loW denier filament is used.

where R and R are hydrocarbon groups such as alkylene and arylene and where X is O or NH. In the case of polyethylene terephthalate R is the paraphenylene group and 3 R is the 1:2 ethylene group. In the case of 66 nylon, R is the tetramethylene group and R is the hexamethylene group. We believe that for an effective treatment the links between the -R.CO and the XR- group in the above formula must be broken.

The treatment may cause hydrolysis as in the case of steam, acids or bases; or it may cause amidation as in the case of ammonia and amines. Suitable amines are mono-, di-, or tri-substituted amines as well as certain amine compounds which can be reacted with the shaped fibre-forming polymers.

The treatment with one or a combination of two or more of the above agents should be continued until the tenacity of a single filament in the yarn is reduced to the specified limits. Alternatively, the molecular weight or intrinsic viscosity of the polymer may be used as a measure of reducing the strength of the filaments. In the case of polyethylene terephthalate the intrinsic viscosity should be reduced to a value below about 0.45, but higher than about 0.25. The breaking load of the individual filaments in the yarns may also be reduced to the specified limits by an intensive radiation treatment including actinic light or corpuscular radiation.

Instead of treating commercially available synthetic yarns to obtain anultimate filament strength in the made up articles within the specified limits of 1-3.5 grams per denier, filaments possessing the required low strength may be produced by the filament yarn manufacturer. In this case, polymers of exactly the same chemical composition as would be used for the commercially available yarns, but which have a lower molecular weight or a lower intrinsic viscosity prior to spinning, should be used. In the case of polyethylene terephthalate, the intrinsic viscosity of the polymer prior to spinning and drawing would be somewhat higher than the intrinsic viscosity obtained in an after-treatment since allowance has to be made for degradation, which takes place between the yarn manufacturing processes and in the subsequent bulking and finishing operations. A suitable range of polyethylene terephthalate polymer prior to spinning lies between an intrinsic viscosity of 0.35 and 0.46, depending, of course, on the manufacturing and finishing conditions and on the filament denier in the yarn.

The tenacity of the bulked yarns may also be reduced by a mechanical treatment. It will be appreciated that the breaking load of the individual filaments will be reduced by mechanical damage and may be caused by severe stressing, compressing, cutting and abradin-g. The filaments become, thereby, weakened at intervals. It is, of course, also possible to provide filaments which are weakened at intervals by spinning filaments of non-uniform cross-section e.g. of filaments with denier variations along their length.

A process for making synthetic polyester bulked yarn filaments comprised treating the filaments with a chemical agent, preferably with sodium hydroxide solution to which there may be added catalytic amounts of quarternary ammonium salts as an accelerator, after stuffer box or gear crimping, but preferably before heat setting the crimp, whereby the filaments become weakened at intervals corresponding substantially to the apexes of their crimp.

The fabrics may be made from false twisted, stufier box crimped or hot wire crimped, bulked filament yarn having the specified tenacity, a yarn crimp elongation of less than 15% and a shrinkage per unit length, in hot water or steam, not exceeding In the case of the false twisted bulked filament yarn, non-torque singles yarn is preferred for knitting.

'Ilhe following Table 1 illustrates the formation of snags and agglomerates on fibres of polyethylene terephthalate knitted fabric (A), which is compared with the same fabric after degradation with steam for six hours at 120 C. (B).

TABLE 1 Number of Agglomerates Per Sq. Inch Time, Mlns.

Untrcated- Treated Tenacity, Tenacity,

4 g.p.d. 2.5 g.p.d.

It will be seen from Table 1, in which the knitted fabric was subjected to a tumbler abrasion test, that the formation of agglomerates is appreciably reduced when the filament strength in the bulked yarn is reduced to a tenacity of 2.5 grams per denier.

The following example illustrates, but does not limit our invention.

Example 1 Polyethylene terephthalate polymer having an intrinsic viscosity (in orthochlorophenol) of 0.43 is melt spun and the filaments are drawn to a draw ratio of 1:365, over a hot pin maintained at C. and passed over an electrically heated wire maintained above the melting temperature of the filaments, positioned between draw rolls and a windup mechanism as described in British Patent 808,213. The wound up potentially crimped filaments are relaxed in air at 205 C. by rewinding using an overfeed of 28%, whereby a bulked yarn is obtained having a filament tenacity of 2.56 grams per denier.

T he bulked yarn is knitted on a 10 gauge flat bed knitting mao'hine. Samples of the fabric are subjected to various abrasion tests as used for the assessment of pilling in spun staple yarn fabrics. In all the tests the formation of agglomerates is considerably reduced, compared with similar fabrics knitted from various bulked yarns having a tenacity between 3.9 and 4.5 grams per denier.

While the invention has been described more particularly with regard to filaments of polyethylene terephthalate it is also applicable to filaments of other polyesters or copolyesters, e.g. wherein the terephthalate acid or the glycol used in making polyethylene terephthalate are replaced at least in part by some other glycol or dibasic acid, such as sebacic or isophthalic, polyamides, polyolefines particularly isotactic polypropylene.

What we claim is:

1. A process for producing a bulked filament yarn for making fabrics having improved wear properties comprising 1) melt spinning and drawing a fibre forming thermoplastic polymer having an intrinsic viscosity between 0.35 and 0.46 selected from the group consisting of polyesters and copolyesters of terephthalic acid when said filaments have an initial tenacity greater than about 4.5 grams per denier, followed by (2) reducing the tenacity of the individual filaments of said yarn when measured at intervals of not more than /1. inch to between 1 and 3.5 grams per denier by treating and bulking the filament yarn by passing the yarn over a narrow heated surface followed by relaxing the yarn, until the desired tenacity is obtained.

2. A process for making fabric from bulked yarn comprising melt spinning polyethylene terephthalate polymer having an intrinsic viscosity in orthochlorophenol of 0.43, drawing the melt spun filaments to a draw ratio of about 1-3.6 over a hot pin maintained at about 90 C. and passing the filaments over an electrically heated wire maintained above the melting temperature of the filaments, relaxing the potentially crimped filaments in air at about 205 C. using an over-feed of about 28% whereby a bulked yarn is obtained having a filament tenacity 5 6 of about 2.5 grams per denier, knitting the bulked yarn 3,025,659 Stoddard et a1 Mar. 20, 1962 into a fabric, said fabric having a considerably reduced 3,069,837 Olson Dec. 25, 1962. tendency to form agglomerates. 3,104,450 Christens et a1. Sept. 24, 1963 References Cited in the file of this patent FOREIGN PATENTS 225,794 Australia Dec. 14, 1959 UNITED STATES PATENTS 576,762 Canada May 26, 1959 9 Hardy et June 1942 579,696 Canada July 14, 1959 2,516,562 Grahamy 25, 1950 1,154,495 France Nov. 4, 1957 2,604,689 Hebeler July 1952 10 (Corresponding Great Britain, 840,796, July 13, 1960) 2,865,080 Hentschel 23, 1953 743,906 re Br tain Jan, 25, 1956 2,869,967 Breen 20, 1959 808,213 Great Britain Jan. 28, 1959 2,917,806 Spence et a1. Dec. 22, 1959 

1. A PROCESS FOR PRODUCING A BULKED FILAMENT YARN FOR MAKING FABRICS HAVING IMPROVED WEAR PROPERTIES COMPRISING (1) MELT SPINNING AND DRAWING A FIBRE FORMING THERMOPLASTIC POLYMER HAVING AN INTRISIC VISCOSITY BETWEEN 0.35 AND 0.46 SELECTED FROM THE GROUP CONSISTING OF POLYESTERS AND COPOLYESTERS OF TEREPHTHALIC ACID WHEN SAID FILAMENTS HAVE AN INITIAL TENACITY GREATER THAN ABOUT 4.5 GRAMS PER DENIER, FOLLOWED BY (2) REDUCING THE TENACITY OF THE INDIVIDUAL FILAMENTS OF SAID YARN WHEN MEASURED AT INTERVALS OF NOT MORE THAN 3/4 INCH TO BETWEEN 1 AND 3.5 GRAMS PER DENIER BY TREATING AND BULKING THE FILAMENT YARN BY PASSING THE YARN OVER A NARROW HEATED SURFACE FOLLOWED BY RELAXING THE YARN, UNTIL THE DESIRED TENACITY IS OBTAINED. 